Flash lamp



Nov. 15, 1966 R. M. ANDERSON FLASH LAMP Filed June 19; 1964 ITWVEBTWTOT. Robewt: MLATJGT'SOTW His t tQVne United States Patent 3,285,035 FLASH LAMP Robert M. Anderson, Euclid, Ohio, assignor to General Electric Company, a corporation of New York Filed June 19, 1964, Ser. No. 376,377 2 Claims. '(Cl. 67-31) This invention relates to photographic flash lamps of the type comprising a sealed bulb or envelope containing a combustion-supporting atmosphere in a loosely arranged filling of metallic combustible material which is ignited by an ignition means comprising a fulminating primer and a filament or heater element adapted to set off the primer. More particularly, this invention relates to a novel construction of the ignition means or mount structure for such flash lamps.

Conventional type flash lamps in common use at present are provided with ignition means customarily comprising a filament consisting of a short length of fine tungsten wire, preferably alloyed with rhenium, usually having an effective lighted length of the order of 50 to 65 mils which is connected across the inner ends of a pair of substantially side-by-side lead-in wires sealed into one end of the bulb. The filament is energized and heated usually by a dry cell battery connected across the lead-in wires to thereby ignite a fulminating primer coated on the inner ends of the lead-in wires at their connections or junctions with the filament. The ignited primer then ignites in turn a filling of filamentary combustible metallic material which produces a momentary flash of light of high intensity with the ensuing combustion thereof.

The assembly of the filament, its supporting lead-in wires and the primer coating on the inner ends of the leadin wires together comprise what is commonly known as the mount structure of the lamp. In the manufacture of the lamp, the mount structure is sealed into the bulb in a position in which the filament and the associated primer coatings or beads are located within the filling of combustible material which is placed in the bulb thereafter so as to be more or less surrounded by the combustible material and thus the mount is in effective ignition range relative to the combustible material. To this end, it is common practice in, for example, manufacture of miniature flash lamps such as the type commonly known as AG1 to first seal the mount structure into one end of an open tube and then to insert the combustible material through the other open end of the tube surrounding said mount structure. With such a procedure the strands of filamentary combustible filling material, or at least some of them within the lamp bulb, usually contact the filament between the two primer beads or coatings. The strands of combustible material thus in contact with the filament then exert a cooling effect thereon during the energization and heating of the filament to set off the primer. This cooling effect on the filament is sufficient in some cases as when the dry cell batteries are weak or the circuit contacts are poor to prevent the filament from attaining a temperature high enough to ignite the primer with the result that the lamp fails to flash. The flashability of the lamp thus is adversely effected by the contact of the ignition filament with the combustible material present within the lamp bulb.

Moreover, the pressure of the combustible material against the fine tungsten-rhenium wire filament with which it is in contact is also apt to cause elongation of the filament during the time it is heating up. The resulting reduction in the cross-sectional area of the filament and the corresponding increase in its electrical resistance at the region of the reduced cross-sectional area therefore tends to cause either the burn-out of hte filament at such 3,285,035 Patented Nov. 15, 1966 region of reduced cross-sectional area or a severing or pulling apart of the filament at such region so that the lamp again in this case fails to flash.

It is an object, therefore, of my invention to provide a mount structure for use in a flash lamp of the above mentioned character having improved flashability characteristics and greater freedom from filament burn-out from lamp to lamp.

Another object of my invention is to provide a flash lamp of the above-mentioned character having an ignition filament located within, but uniformly protected from, contact with the filamentary combustible material in a consistent manner.

Briefly stated, in accordance with one aspect of the invention, the primer coated inner ends of the lead-in wires of conventional type lamp ignition mounts such as have been customarily used heretofore in flash lamps across which lead-in wires and the ignition filament is connected are provided with protective means on its inner ends to prevent or minimize contact of the filamentary combustible material with the ignition filament. A preferred structure for such protective means provides a protective cap over the filament by bending at least one of the lead-in wires at substantially right angles to the lead-in wire in a direction such that it is generally parallel to and dis-posed over the filament to cover the filament relative to the combustible material in the lamp.

Further objects and advantages of the invention will appear from the following detailed description and from the accompanying drawings wherein:

FIG. 1 is an elevation of a flash lamp of one embodiment of my invention;

FIG. 2 is a greatly enlarged fragmentary elevation of the ignition means or mount structure of the flash lamp shown in FIG. 1; and

FIGS. 3, 4 and 5 are mount structures showing further embodiments of the invention.

Referring to the drawing, FIG. 1, the flash lamp there shown comprises a sealed light-transmissive envelope or bulb 1 which may be formed of glass and contains a filling of combustion-supporting gas such as oxygen and a loosely arranged filling of filamentary metallic combustible material 2 of a composition such as zirconium, aluminum or aluminum magnesium alloy which is of a readily combustible character when in a finely divided or filamentary state. As shown, the combustible material may be in the form of a fine wire, ribbon or other filamentary character such as that commonly known as shedded foil, the individual strand of the filamentary material having a cross-sectional area of the order of 1 square rnil.

Sealed into a pressed end 4 of the envelope or bulb 1 is a lamp ignition means or mount structure comprising a pair of lead-in wires 5 extending through the press end 4 and maintained in a predetermined spaced arrangement by a glass head 6. As shown, the lead-in wires 5 extend from the flattened press end 4 into the interior of the envelope or bulb 1 in more or less side-by-side relation and they are bridged at their inner ends by a filament 8 in the form of a straight length of fine tungstenrhenium wire, usually of 1 mil or less diameter, preferably approximately A mil.

Connected to the respective lead-in wires 5 and located within the range of the filling of combustible material 2 so as to be in effective ignition relation thereto, the filament 8 has an effective lighted length between its connections to the lead-in wires of approximately 55 to 60 mils, such as has been customary heretofore. The inner ends of the lead-in wires 5 at their junctions or connections with the ignition filament 8 are provided with thin coatings or beads 9 of a suitable primer of fulminating material such as a mixture of Zirconium magnesium and potassium perchlorate powders bonded together with a suitable binder such as a 2 to 8% solution of nitrocellulose in amyl acetate. Exteriorly of the envelope or bulb 1, the lead-in wires are bent in loops 7 with the ends thereof re-entered into the stem press 4 and form re-entrant contact members as is conventional. The envelope or bulb 1 may be exhausted and filled with oxygen or other combustion supporting gas in a conventional manner through an exhaust tip 13 extending from the upper end of said envelope or bulb 1. After evacuation of the envelope 1 and the introduction of the gas filling thereto, the upper end of the lamp is tipped off in a well known manner to thereby hermetically seal the envelope.

When the combustible material is inserted in the prior art lamps around the ignition mount structure which has been sealed in the press end 4 of the lamp, the strands of combustible material, or at least some of them, come in contact with the filament 8 and it has been noted to greatly decrease the flashability thereof.

The ignition mount structure in accordance with the invention is provided with means for preventing the filamentary combustible material from contacting the filament. This covering or prevention means, as shown in FIG. 2, comprises an extension of the lead-in wires 5 which are then bent over toward each other so that the primer heads 9 substantially bridge the gap between the ends, thus greatly reducing the opening between leadin wire tips and greatly minimizing the possibility of the filamentary combustible material contacting the filament. Flash lamps constructed in accordance with FIG. 2 have been found to exhibit 50% greater flashability on weak or low current flashing conditions as shown by the following chart:

Example No. No. in Example Percent Lamp Flashed All of the above even-numbered tests were of standard construction, and the odd numbered tests were of lamps of the invention. Examples 1 and 2 (also 9 and 10, below) were controlled laboratory tests, while Examples 3 through 8 (also 11 through 16, below) were in actual camera tests. I

In constructing the lamps of the type shown in FIG. 2, it-has been found that the removal of the filament to a spacing which is further away, i.e., at least 75 mils, from the inner ends of the lead-in wires greatly enhances the fiashability of the lamps even where a more definite protective cap means is not provided. A construction of this type referred to is shown in FIG. 3 wherein lead wires 15 extend beyond filament 18 a distance which is greater than the distance between lead wires. The results of tests on the flashability of these lamps (odd numbers) with respect to conventional ignition mount construction (even numbers) is shown as follows:

Other means for obtaining a cap or preventive filament construction are shown in FIGS. 4 and 5. In FIG. 4, a lead wire 25 of the type shown in FIG. 2 is provided while another lead wire 25a is bent over parallel to and disposed over the filament 28 to substantially bridge the gap, forming a protective cap over the filament to prevent contact of the combustible material with the filament. In FIG. 5, a more conventional lead wire 35 is provided while another lead wire 35a has a bent over portion parallel to the filament 38 and its outer end bent downwardly to line up with the end of lead wire 35. The flashability of these constructions was also found to be at least 50% better than standard construction.

From the above tests it will be noted that the fiashability of the lamps has been greatly enhanced by shielding the filament from contact with the filamentary combustible material in some manner, either by a definite primer bridge or a bent-over lead-in wire or by merely spacing the filament further from the ends of the lead-in wires. This is believed to be because of the fact that the contact of the combustible filamentary material with the filament removes heat therefrom although it may be in part due to short circuiting of the filament by the combustible material being in contact with a portion of the filament and the lead-in Wires. Whatever the explanation, it would appear that the lamps provided with some means for preventing the firm contact of the filamentary combustible material with the ignition filament greatly enhances flashability.

Although the preferred embodiments of my invention have been disclosed, it will be understood that the invention is not to be limited to the specific construction and arrangement of parts shown but that they may be widely modified within the spirit and scope of the invention as defined in the appended claims. For example, while the primer beads are shown as covering the protective inner ends of the lead wires, this would not be necessary and the ends could be left bare or cleaned and still provide greater flashability of the lamps.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A flash lamp comprising a sealed envelope hava ing an oxidizing atmosphere therein, a quantity of readily combustible filamentary material loosely arranged within said envelope and ignition means disposed in said envelope within effective ignition range of said combustible material, said ignition means comprising a filament connected across a pair of lead-in wires and coatings of a fulrninating substance on said lead-in wires and embedding portions of said filament, wherein: an end of at least one of said lead-in wires is bent at substantially right angles to the lead-in wire in a direction such that it is generally parallel to and disposed over the filament to cover the filament relative to said combustible material, forming a protective cap over the filament to prevent contact of said combustible material with said filament.

2. A flash lamp as recited in claim 1, wherein said combustible filamentary material consists essentially of zirconium, and said fulminating substance comprises a powder admixture of magnesium, zirconium and potassium perchlorate.

References Cited by the Examiner UNITED STATES PATENTS 2,783,632 3/1957 Eppig 67-3l 3,046,770 7/ 1962 Anderson 67-31 3,218,832 11/1965 Seidler 6731 FOREIGN PATENTS 831,391 3/ 1960 Great Britain.

FREDERICK L. MATTESON, JR., Primary Examiner. ROBERT A. DUA, Examiner. 

1. A FLASH LAMP COMPRISING A SEALED ENVELOPE HAVING AN OXIDIZING ATMOSPHERE THEREIN, A QUANTITY OF READILY COMBUSTIBLE FILAMENTARY MATERIAL LOOSELY ARRANGED WITHIN SAID ENVELOPE AND IGNITION MEANS DISPOSED IN SAID ENVELOPE WITHIN EFFECTIVE IGNITION RANGE OF SAID COMBUSTIBLE MATERIAL, SAID IGNITION MEANS COMPRISING A FILAMENT CONNECTED ACROSS A PAIR OF LEAD-IN WIRES AND COATINGS OF A FULMINATING SUBSTANCE ON SAID LEAD-IN WIRES AND EMBEDDDING PORTIONS OF SAID FILAMENT, WHEREIN: AN END OF AT LEAST ONE OF SAID LEAD-IN WIRES IS BENT AT SUBSTANTIALLY RIGHT ANGLES TO THE LEAD-IN WIRE IN A DIRECTION SUCH THAT IT IS GENERALLY PARALLEL TO AND DISPOSED OVER THE FILAMENT TO COVER THE FILAMENT RELATIVE TO SAID COMBUSTIBLE MATERIAL, FORMING A PROTECTIVE CAP OVER THE FILAMENT TO PREVENT CONTACT OF SAID COMBUSTIBLE MATERIAL WITH SAID FILAMENT. 